FUEL SUPPLY SYSTEM FOR ENGINE

Abstract

When a flywheel rotates and a first magnet comes close to and opposes a fuel pump, a plunger is moved toward a partition wall of a pump chamber against an urging force of a spring by a magnetic repulsive force generated between the first magnet and a second magnet in the fuel pump. When the first magnet separates from the fuel pump, the plunger is moved and returned toward a protective cover by the urging force of the spring. As a result, the plunger in the fuel pump reciprocates with rotation of the flywheel, and the capacity of the pump chamber increases and decreases, so that fuel is sucked and discharged.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS

The disclosure of Japanese Patent Application No. 2009-024930 filed on Feb. 5, 2009 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a fuel supply system for an engine, which pressurizes fuel from a fuel tank and supplies the fuel to a fuel injection valve without using driving power from a battery.

2. Description of the Related Art

In most general-purpose engines of a spark ignition type for use in power generators and operating machines, a battery is not mounted, starting is performed by manually pulling a recoil starter, and power for ignition is supplied by a magneto. In a case in which the amount of fuel injected from a fuel injection valve provided in such a general-purpose engine is electronically controlled in accordance with the operating condition of the engine, it is a problem how to ensure power for the devices.

In this case, the fuel injection valve and an electronic control device for controlling the fuel injection valve can be driven by the voltage provided immediately after starting is performed by pulling the recoil starter. However, it is difficult to ensure sufficient power for a fuel pump for generating fuel pressure that is the point of fuel control. For this reason, there is no other choice but to use, as the fuel pump, a mechanical fuel pump that is driven by the engine.

For example, in a battery-less electronic fuel injection control device disclosed in Japanese Unexamined Patent Application Publication No. 5-164010, fuel is pressurized by a mechanical pump that is driven in conjunction with the rotation of a flywheel connected to a crankshaft of the engine, and the fuel is then supplied to a fuel injection valve.

Japanese Examined Utility Model Registration Application Publication No. 7-52374 discloses a technique using a film-valve pulse pump for pressurizing and supplying fuel by the change in internal pressure of a crankcase, and a plunger-type fuel pump to be driven by a cam attached to a crankshaft. Fuel in a fuel tank is pressure-fed to the plunger-type fuel pump by the film-valve pulse pump, is further pressurized by the plunger-type fuel pump, and is then supplied to a fuel injection valve.

However, in the mechanical fuel pump driven by the engine, the mechanism is complicated to obtain a stable pressure suitable for fuel injection, and this leads to a rise in cost. Moreover, the performance may be reduced by the influences of trouble and heat.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above-described circumstances, and an object of the invention is to provide an engine fuel supply system capable of obtaining a stable pressure suitable for fuel injection.

In order to achieve the above object, an engine fuel supply system according to the present invention pressurizes fuel from a fuel tank and supplies the pressurized fuel to a fuel injection valve without using driving power from a battery. The engine fuel supply system includes a first magnetic member fixed to an outer peripheral portion of a rotor connected to a rotation shaft of an engine; and a fuel pump opposing the outer peripheral portion of the rotor and including a second magnetic member that magnetically acts on the first magnetic member. At least one of the first magnetic member and the second magnetic member is formed by a permanent magnet. The fuel pump reciprocates the second magnetic member by a magnetic force between the first magnetic member and the second magnetic member, the magnetic force changing with rotation of the rotor, and sucks the fuel from the fuel tank and discharges the fuel with a predetermined pressure by the reciprocation.

According to the present invention, it is possible to obtain a stable pressure suitable for fuel injection without using a complicated mechanism, and to thereby realize an inexpensive fuel supply system with high reliability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structural view of an engine fuel supply system; and

FIG. 2 is an enlarged view showing an exemplary structure of a fuel pump.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention will be described below with reference to the drawings.

An engine 1 shown in FIG. 1 is a general-purpose engine of a spark ignition type, and is used as, for example, a motor for a power generator, an operating machine, or a snowmobile. In FIG. 1, the engine 1 is an air-cooled V-engine, in which a suction port 4 and an exhaust port 5 are open in a cylinder head 3a provided in an upper part of a cylinder 3 inclined with respect to a crankcase 2. The suction port 4 communicates with an air cleaner (not shown), and the exhaust port 5 communicates with a muffler 6 provided above the cylinder head 3a.

A crankshaft 1a protrudes from the crankcase 2 of the engine 1. The crankshaft 1a is connected, via a connecting rod, to a piston that slidably reciprocates in the cylinder 3, and is rotatably supported by the crankcase 2. A cooling fan 7 is fitted on and rotatably supported by a protruding shaft of the crankshaft 1a. On the circumference of the cooling fan 7, a plurality of fins 7a are arranged at regular intervals. A flywheel 9 (see FIG. 2) is provided integrally with a back side of the cooling fan 7. A magnet (permanent magnet) 8 for ignition is fixed to an outer peripheral portion of the flywheel 9.

A control unit 10 and a fuel pump 20 are provided beside the cooling fan 7 of the crankcase 2 in a manner such as to face the magnet 8 of the flywheel 9 with a predetermined gap being therebetween. The control unit 10 includes a magneto coil and an ignition coil facing the magnet 8 of the flywheel 9 with a predetermined gap being therebetween, an ignition circuit, such as a transistor or a mechanical contact, for energizes and interrupts one side of the ignition coil, a power supply circuit for generating control power by rectifying and smoothing magneto power, and an electronic control circuit for engine control that mainly includes a microcomputer.

An ignition plug 11 is connected to an output side of the ignition circuit incorporated in the control unit 10. The ignition plug 11 is provided in the cylinder head 3a, and has, at its leading end, a discharging electrode exposed in a fuel chamber. Further, an injector (fuel injection valve) 12 is connected to an output side of the electronic control circuit incorporated in the control unit 10. The injector 12 injects fuel, which is press-fed from the fuel pump 20, into a suction passage of the engine 1.

In FIG. 1, for convenience of understanding of the fuel supply system, the injector 12 that is actually provided near the suction port 4 of the engine 1 is shown separately from the engine 1.

Next, a description will be given of the fuel pump 20 that is a major component of the fuel supply system. The fuel pump 20 includes a suction-side joint portion 21a serving as a fuel suction port, a discharge-side joint portion 21b serving as a fuel discharge port, and flange portions 21c serving portions mounted to the crankcase 2. The suction-side joint portion 21a is connected to a fuel tank 14 via a pipe 13, and the discharge-side joint portion 21b is connected to the injector 12 via a pipe 15.

A fuel filter 16 is interposed in the pipe 13 that connects the fuel tank 14 and the fuel pump 20, and a pulsation damper 17 for damping pulsation of fuel pressure is interposed in the pipe 15 that connects the fuel pump 20 and the injector 12. For example, the fuel tank 14 is provided above the engine 1.

As will be described below, a first magnetic member is fixed to an outer peripheral portion of a rotor that is connected to the crankshaft 1a serving as the rotation shaft of the engine 1, and the fuel pump 20 includes a second magnetic member that can magnetically act on the first magnetic member. At least one of the first magnetic member and the second magnetic member is formed by a permanent magnet. The fuel pump 20 is a reciprocating pump that is operated by magnetic force of the permanent magnet in a non-contact manner.

In the embodiment, as illustrated in FIG. 2, the first magnetic member is the ignition magnet (permanent magnet) 8 fixed to the outer peripheral portion of the flywheel 9 serving as the rotor connected to the crankshaft 1a, and the second magnetic member is a magnet (permanent magnet) 31 fixed to a plunger 30 in the fuel pump 20. The fuel pump 20 is a plunger-type pump in which the plunger 30 reciprocates by magnetic forces of the magnets 8 and 31 with rotation of the flywheel 9.

More specifically, the fuel pump 20 includes a pump housing 21 and a protective cover 22. The suction-side joint portion 21a, the discharge-side joint portion 21b, and the flange portions 21c for mounting are provided outside the pump housing 21, and the plunger 30 is provided in the pump housing 21 in a manner such as to move forward and backward. The protective cover 22 covers an opening provided in a side of the pump housing 21 opposite the suction-side joint portion 21a and the discharge-side joint portion 21b. The pump housing 21 is formed of a nonmagnetic material such as aluminum, and the protective cover 22 is formed of a magnetically permeable material such that the magnetic force from the magnet 8 of the flywheel 9 acts on the interior of the fuel pump 20.

The pump housing 21 includes a pump chamber 23 accommodating the plunger 30, a suction-valve chamber 25 accommodating a check valve 24 that transmits fuel from the suction-side joint portion 21a only toward the pump chamber 23, and a discharge valve chamber 27 accommodating a check valve 26 that transmits fuel from the pump chamber 23 only toward the discharge-side joint portion 21b.

The plunger 30 is shaped like a hollow cylinder having one closed end, and the magnet (permanent magnet) 31 is fixed to the closed end. The plunger 30 is provided in the pump chamber 23 with the magnet 31 facing the protective cover 22 in a manner such as to move into and out of the pump chamber 23. A spring 28 for urging the plunger 30 toward the protective cover 22 is provided between a back surface of the closed end in the plunger 30 and a partition wall 23a for the valve chambers 25 and 27 of the pump chamber 23. Further, a seal member 29, such as an O-ring or an oil seal, is provided on an inner peripheral surface of the cylinder of the pump chamber 23. The seal member 29 serves to maintain oil tightness between the inner peripheral surface of the pump chamber 23 and an outer peripheral surface of the cylinder of the plunger 30.

The magnet 31 fixed to the plunger 30 and the magnet 8 fixed to the outer peripheral portion of the flywheel 9 are set in a manner such that the same poles thereof oppose each other.

The fuel pump 20 having the above-described configuration is located such that the moving axis direction of the plunger 30 points toward the rotation center of the flywheel 9 and such that a specified distance is provided between the fuel pump 20 and the magnet 8 of the flywheel 9. The fuel pump 20 is fixed to the crankcase 2 by bolts with the flange portions 21c being disposed therebetween. Next, a description will be given of how the engine 1 is driven by the fuel supply from the above-described fuel pump 20.

First, when the flywheel 9 is rotated by pulling the recoil starter (not shown), the magnet 8 fixed to the outer peripheral portion of the flywheel 9 circles to pass across the fronts of the control unit 10 and the fuel pump 20. Then, control power is generated from magnet power that is produced by the rotation of the flywheel 9, and operates the ignition circuit and the electronic control circuit in the control unit 10.

In this case, at a position where the magnet 8 of the flywheel 9 is located close to and opposes the fuel pump 20, the plunger 30 having the magnet 31 fixed thereto moves toward the partition wall 23a of the pump chamber 23 against the urging force of the spring 28 because of magnetic repulsive force generated between the magnet 8 of the flywheel 9 and the magnet 31 in the fuel pump 20. In contrast, when the magnet 8 separates from the fuel pump 20, the repulsive force between the magnets 8 and 31 reduces or disappears, so that the plunger 30 moves and returns toward the protective cover 22 because of the urging force of the spring 28.

As a result, with the rotation of the flywheel 9, the plunger 30 in the fuel pump 20 reciprocates toward the partition wall 23a and the protective cover 22, whereby the capacity of the pump chamber 23 increases and decreases to suck and discharge the fuel. In other words, when the plunger 30 moves toward the protective cover 22, the capacity of the pump chamber 23 increases, the pressure in the pump chamber 23 decreases, the check valve 24 of the suction valve chamber 25 opens, so that fuel is sucked from the fuel tank 14 into the pump chamber 23 through the suction-side joint portion 21a. The fuel in the pump chamber 23 is pressurized by the movement of the plunger 30 toward the partition wall 23a, and the check valve 26 of the discharge valve chamber 27 opens at a predetermined pressure, so that the fuel is discharged from the discharge-side joint portion 21b and is supplied to the injector 12.

Then, the injector 12 is driven to inject the fuel at a valve opening time calculated by a CPU of the electronic control circuit in the control unit 10. Further, the ignition plug 11 sparks in response to a signal from the ignition circuit, and a mixture of the fuel injected from the injector 12 and the sucked air is ignited and burnt, whereby the engine 1 is driven.

In this way, in the embodiment, the fuel supply system for supplying the fuel to the injector 12 is configured by utilizing the magnet 8 fixed to the outer peripheral portion of the flywheel 9 of the magneto ignition engine. That is, it is possible to realize an inexpensive fuel supply system in which the plunger 30 of the fuel pump 20 reciprocates by a magnetic force of the ignition magnet 8 with the rotation of the flywheel 9.

In the fuel pump 20 of this fuel supply system, there is no need to obtain pump driving force by mechanical connection to the rotation shaft of the engine, a stable driving force can be obtained without contact with the rotating section of the engine, and a stable pressure suitable for fuel injection can be obtained. In addition, since the pump is driven without contact with the rotating section of the engine, it is possible to suppress performance degradation due to trouble and heat, and to realize an inexpensive fuel supply system with high reliability.

The fuel pump 20 that constitutes of the fuel supply system in the above-described embodiment is just exemplary, and various other modifications are possible. For example, the fuel supply system can have the following configurations (1) to (3):

(1) The magnet 31 fixed to the leading end of the plunger 30 in the fuel pump 20 and the magnet 8 fixed to the outer peripheral portion of the flywheel 9 are set in a manner such that opposite poles thereof face each other, and the spring 28 for urging the plunger 30 is formed by a tension spring.

(2) The magnet 31 fixed to the leading end of the plunger 30 in the fuel pump 20 is eliminated, and a magnetic member, such as a steel member, is fixed to the leading end of the plunger 30. Alternatively, the plunger 30 itself is formed by a magnetic material. Also, the spring 28 for urging the plunger 30 is formed by a tension spring.

(3) The fuel pump 20 is formed by a reciprocating pump using a diaphragm, instead of the plunger 30.

Claims

1. An engine fuel supply system that pressurizes fuel from a fuel tank and supplies the pressurized fuel to a fuel injection valve, the engine fuel supply system comprising:

a first magnetic member fixed to an outer peripheral portion of a rotor connected to a rotation shaft of an engine; and

a fuel pump opposing the outer peripheral portion of the rotor and including a second magnetic member that magnetically acts on the first magnetic member,

wherein at least one of the first magnetic member and the second magnetic member is formed by a permanent magnet, and

wherein the fuel pump reciprocates the second magnetic member by a magnetic force between the first magnetic member and the second magnetic member, the magnetic force changing with rotation of the rotor, and sucks the fuel from the fuel tank and discharges the fuel with a predetermined pressure by the reciprocation.

2. The engine fuel supply system according to claim 1, wherein the first magnetic member is a permanent magnet for generating ignition power.

3. The engine fuel supply system according to claim 1, wherein the fuel pump is a plunger-type pump that sucks and discharges the fuel by reciprocating a plunger including the second magnetic member.